1. Field of Invention
The present invention relates to protective structures for vehicular engine parts, such as engine exhaust manifolds for example, that generate substantial heat and vibration during engine operation. More particularly, the invention relates to fabrication of protective heat shields applied to engine parts for insulating such parts from other components within an engine compartment of a vehicle.
2. Description of the Prior Art
The exhaust manifolds of internal combustion engines in today""s modern vehicles can reach under-the-hood temperatures in the neighborhood of 1600 degrees Fahrenheit. Such high temperatures create significant risks of damage to electronic components sharing under the hood space with the manifolds. Thus protection has been provided for such components via use of heat shields designed to cover up, and hence insulate, exhaust manifolds and other heat generating components. In some cases, the shields have been effective to reduce measured temperature levels to within a range of 300 degrees Fahrenheit, along with substantial commensurate reductions in noise levels. Typical heat shields, however, comprise at least two metal layers that sandwich an installation layer. The metal layers are created from single layer blanks by so-called forming dies.
The forming dies used to manufacture the metal heat shield layers are prone to creating winkles at rounded edges of the metal layers where the layers are subject to highest stresses within the dies. The wrinkled edges represent plastically deformed, crushed together portions in which the yield strength of the metal has been exceeded. Such portions are subject to cracks, and give rise to crack propagation issues. The crushed together portions also define thicker portions in the shield body that are stiffer and more prone to producing echoes rather than to absorbing vibrations and/or noise.
The present invention provides an improved insulated heat shield for engine components, such as exhaust manifolds of internal combustion engines. In the described embodiment, a heat shield is formed as a unitary structure adapted for securement via bolted connections to an engine manifold.
In the described embodiment, the shield includes three layers; an outer metal layer to provide overall structural integrity, a center layer formed of an insulation material to isolate heat and to dampen noise, and an inner metal layer adjacent the shielded component for reflecting heat back to the shielded component.
Also in the described embodiment, the edges of the metal layers are defined by outwardly flared undulations or waves to minimize stiffness produced by plastic deformation that occurs in the edges of the layer during manufacture of the shield. In addition, the waved edges are folded over to avoid cutting hands and/or fingers of installers or assemblers, or even under-the-hood wiring and hose structures. The folded edges also provide reinforcement of the composite heat shield structures, and thus serve to optimize useful life. Finally, a system of integrally incorporated beads in the metal layers is effective to provide selective stiffness in regions of the layer where needed.